linux-kernel - Re: [PATCH v8 01/16] PCI/CXL: Introduce PCIe helper function pcie_is

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Message-ID: <9d0636f0-784b-4074-9364-45b2377947d9@amd.com>
Date: Thu, 27 Mar 2025 10:30:48 -0500
From: "Bowman, Terry" <terry.bowman@....com>
To: Ira Weiny <ira.weiny@...el.com>, linux-cxl@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
 nifan.cxl@...il.com, dave@...olabs.net, jonathan.cameron@...wei.com,
 dave.jiang@...el.com, alison.schofield@...el.com, vishal.l.verma@...el.com,
 dan.j.williams@...el.com, bhelgaas@...gle.com, mahesh@...ux.ibm.com,
 oohall@...il.com, Benjamin.Cheatham@....com, rrichter@....com,
 nathan.fontenot@....com, Smita.KoralahalliChannabasappa@....com,
 lukas@...ner.de, ming.li@...omail.com, PradeepVineshReddy.Kodamati@....com
Subject: Re: [PATCH v8 01/16] PCI/CXL: Introduce PCIe helper function
 pcie_is_cxl()



On 3/27/2025 10:11 AM, Ira Weiny wrote:
> Terry Bowman wrote:
>> CXL and AER drivers need the ability to identify CXL devices.
>>
>> Add set_pcie_cxl() with logic checking for CXL Flexbus DVSEC presence. The
>> CXL Flexbus DVSEC presence is used because it is required for all the CXL
>> PCIe devices.[1]
>>
>> Add boolean 'struct pci_dev::is_cxl' with the purpose to cache the CXL
>> Flexbus presence.
>>
>> Add function pcie_is_cxl() to return 'struct pci_dev::is_cxl'.
>>
>> [1] CXL 3.1 Spec, 8.1.1 PCIe Designated Vendor-Specific Extended
>>     Capability (DVSEC) ID Assignment, Table 8-2
>>
>> Signed-off-by: Terry Bowman <terry.bowman@....com>
>> ---
>>  drivers/pci/pci.c             |  5 +++++
>>  drivers/pci/probe.c           | 10 ++++++++++
>>  include/linux/pci.h           |  3 +++
>>  include/uapi/linux/pci_regs.h |  8 +++++++-
>>  4 files changed, 25 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>> index 869d204a70a3..a1d75f40017e 100644
>> --- a/drivers/pci/pci.c
>> +++ b/drivers/pci/pci.c
>> @@ -5032,6 +5032,11 @@ static u16 cxl_port_dvsec(struct pci_dev *dev)
>>  					 PCI_DVSEC_CXL_PORT);
>>  }
>>  
>> +inline bool pcie_is_cxl(struct pci_dev *pci_dev)
>> +{
>> +	return pci_dev->is_cxl;
>> +}
> Shouldn't this just be a static inline in include/linux/pci.h?
Ok, I'll make that change.
>> +
>>  static bool cxl_sbr_masked(struct pci_dev *dev)
>>  {
>>  	u16 dvsec, reg;
> [snip]
>
>> @@ -741,6 +742,8 @@ static inline bool pci_is_vga(struct pci_dev *pdev)
>>  	return false;
>>  }
>>  
>> +bool pcie_is_cxl(struct pci_dev *pci_dev);
>> +
>>  #define for_each_pci_bridge(dev, bus)				\
>>  	list_for_each_entry(dev, &bus->devices, bus_list)	\
>>  		if (!pci_is_bridge(dev)) {} else
>> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
>> index 3445c4970e4d..7ccb3b2fcc38 100644
>> --- a/include/uapi/linux/pci_regs.h
>> +++ b/include/uapi/linux/pci_regs.h
>> @@ -1208,9 +1208,15 @@
>>  #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL		0x00ff0000
>>  #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_NEXT_INDEX	0xff000000
>>  
>> -/* Compute Express Link (CXL r3.1, sec 8.1.5) */
>> +/* Compute Express Link (CXL r3.1, sec 8.1)
> 				r3.2
>
>> + *
>> + * Note that CXL DVSEC id 3 and 7 to be ignored when the CXL link state
>> + * is "disconnected" (CXL r3.1, sec 9.12.3). Re-enumerate these
>                              r3.2
> Same sections.  :-D

Got it. I'll change the spec release to 3.2.
> With changes:
>
> Reviewed-by: Ira Weiny <ira.weiny@...el.com>
>
> Ira
>
> [snip]
Thanks Ira.